Cathode ray apparatus



Jan. 30, E940. E. Busse 2,188,647

CATHODE RAY APPARATUS Filed Feb. 15, 193e ATTORNEY atented jan. 30, 1946 vPATIENT ori-*ica CATHODE RAY APPARATUS Ernst Busse, Hamburg,

Germany, assignor, by

mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application February 15,

In Germany Februaryl,

7 Claims. (Cl. '25o-27) My present invention relates to a television cathode ray tube and more particularly to a method and an arrangement for supplying anode voltage to a. television cathode ray tube by means of a rectified and smoothed alternating current.

For the operation of a television cathode 'ray tube a weak high voltage current is usually required as anode current. In most cases this current is obtained by applying the alternating current ofga power net-work to a transformer having a suitable transformation ratio and by sub# sequently rectifying and smoothing the high voltage alternating current obtained in this manner. With these hitherto usual arrangements comparatively large smoothing condensers are necessary on account of the low frequency of the alternating current. Due to the large quantities of energy stored in these large condensers severe injuries and even death of persons fortuitously touching voltage carrying parts `may occur.

It is the object of my invention to avoid the danger involved by touching voltage carrying parts in a supply circuit of a television cathode ray tube.

Another object of my invention is to reduce the size of the smoothing means necessary in a supply circuit of a television cathode ray tube.

Still other objects of my invention will be found in the accompanying specification and claims.

To reduce the size of the smoothing means it has been known in the prior art to raise the frequency of the alternating feed current. If, however, the smoothing means are made so extremely small as is required for realizing the objects of my invention, a ripple voltage due to insuflicient smoothing still occurs .in the output of the smoothing circuit, this ripple voltage causing disturbing brightness variations in theteievision picture and moreover, variation in the deflection sensitivity. Owing to the variations of the deection sensitivity the line and point position will be shifted.

According to my invention these disadvantages are avoided by employing as a feed current an alternating current of which the frequency stands in a simple-preferably an integral-re lation to the line deflection frequency.

If, for instance, the frequency of the alternating feed current is made equal to the line deiiection frequency, the alternating feed current being rectified after step up transformation, and subsequently smoothed by extremely small smoothing means, voltage variations in the 1936, Serial No. 64.003 1935 rhythm of the line deflection frequency will still occur in the output of the smoothing circuit. Due to these voltage variations one side of the picture will appear to be slightly darker than the rest of the picture. This would not be disturbing however, if the screen is suitably constructed. On the other hand the positions and the lines and points would be slightly changed in this darker part of the picture. Since, however, this position variation is confined to the same part of the picture it may be readily compensated by suitable measures, for instance by\ a suitable design of the deflections means. In this manner very small smoothing condensers will be sufficient, so that a fortuitous contact with the supply circuit needs no longer be dargerous to life. l

In one embodiment of my invention the saw tooth generator for producing the line deflection frequency also supplies the alternating feed current for the anode of the cathode ray tube.

In another embodiment of my invention a suitable mechanical or electric coupling is provided between the line deflection generator and the feed current generator.

Still another embodiment of my invention comprises a resonance circuit sharply tuned to the frequency of the alternating feed current and being coupled to the feed current generator. Preferably this resonance circuit is so designed that in the case of contact with one of its parts a strong detuning occurs by which the voltage in the circuit drops immediately in a known manner.

My invention will be more readily understood by reference to the accompanying drawing in which a specific embodiment of my invention is shown.

Referring to the drawing there is represented a radio receiver I, to which signals are fed by means of an antenna 2. The radio receiver I may comprise any number of radio frequency amplifier stages, followed by a first detection and by a plurality of intermediate frequency amplifier stages, as is well known in the art. The last tube of the radio receiver I will be a second detector and the output of this second detector is fed to a filter F, which separates the picture currents from the synchronizing impulses. The picture currents are amplified in a picture current amplifier PCA and are subsequently applied to the control grid of a cathode ray tube CRT. The cathode ray tube CRT comprises the usual electrongun and a pair of horizontal and vertical deflection coils. As the construction of television cathode ray tubes is well known in the art and. forms no part of the present invention, the tube is not described more extensively.

The synchronizing impulses are fed from the iilter F to an amplitude filter AF which separates the line and picture frame impulses from each other. The line impulses are fed to a horizontal saw tooth generator 3 and synchronize this generator with the generator used in the transmitter. In the same'manner the pictureeframe synchronizing impulses synchronize the vertical saw tooth generator 4. The output of the generator 3 is fed to the horizontal deflecting coils 5, while the output of the generator 4 is fed to the vertical deecting coils 6.

A part of the output of the horizontal saw tooth generator 3 is supplied to a frequency divider FD, which may be any frequency dividing arrangement known in the art. The frequency divider FD produces an alternating feed current of which the frequency stands in a simple constant relation to the line deflection frequency. The output of the frequency divider FD is transformed to the required voltage by a step up transformer 8 and subsequently rectified by a. diode 9 and smoothed by a smoothing circuit l0, comprising extremely small smoothing condensers on the order of 100 micromicro-farad capacity. The output voltage of the smoothing circuit i is fed to the anode 1 and to the second anode Il of the cathode ray tube.

While I have described and indicated a system for carrying my invention into effect, it will be apparent to one skilled in the art that my invention is by no means limited to the particular embodiment shown and described, but that many modifications may be made without departing from the scope of my invention, as set forth in the appended claims.

What I claim is:

1. In television apparatus wherein is provided a cathode ray tube having an anode, the method of energizing the anode of the cathode ray tube which comprises the steps of generating a sawtooth wave voltage of predetermined frequency, deriving a portion of the generated energy, converting the derived energy to energy of a frequency bearing -harmonic relation to the generated energy, rectifying the converted energy, illtering the rectified energy and supplying the illtered energy to the anode.

2. In a television system wherein is provided a`v cathode ray tube having an anode, the method of energizing the anode, which comprises the steps of generating saw-tooth wave energy of predetermined frequency, deriving a portion of the generated energy, converting the derived portion of the generated energy to energy of a frequency bearing an harmonic relation to the generated energy, rectifying the converted energy, filtering the rectified energy, supplying the ltered energy to the anode, and reducing the value of the energy in accordance with variation of stray capacities in the system.

3. A television system comprising a cathode ray tube having an anode, a saw-tooth wave oscillator of predetermined frequency for deiiectlng a beam of electrons to be generated within said cathode ray tube, means for deriving energy from the saw-tooth wave oscillator, means for converting the derived energy to energy bearing a harmonic relationship to the frequency of the saw tooth oscillator, and means for feeding the convertedv energy to the anode of the cathode ray tube.

4. A television system comprising a cathode ray tube having an anode, a saw-tooth wave oscillator of predetermined frequency for deiiecting a beam of electrons to be generated within said cathode ray tube, means for deriving energy from the saw-tooth wave oscillator, means for converting the derived energy to energy bearing a. harmonic relationship to the frequency of the saw-tooth oscillator, means to rectify the converted energy, means to filter the rectified energy, and means to supply the rectified energy to the anode of the cathode ray tube.

5. A television system comprising a cathode ray tube having an anode, a saw-tooth wave oscillator of predetermined frequency for deecting a beam of electrons to be generated within said cathode ray tube, means for deriving energy from the saw-tooth wave oscillator, means for converting the derived energy to energy bearing a harmonic relationship to the frequency of the saw-tooth oscillator, means to rectify the converted energy, filtering means including condensers of very small capacity for smoothing the rectified energy, and means to supply the ltered energy to the anode.

6. Television apparatus comprising a cathode ray tube having an anode, a saw-tooth oscillator, synchronizing means for controlling, the frequency of the saw-tooth oscillator, means for deriving energy from the saw-tooth oscillator, means for rectifying the derived energy, resonant circuit means for filtering the rectified derived energy, said circuit means being detuned in event of contact by a. person, and means for supplying the filtered energy to the anode.

'7. A cathode ray tube system, comprising a cathode ray tube having a beam of electrons and an anode, a saw-tooth Wave oscillator of predetermined frequency for deecting the beam of electrons, means to derive a portion of the sawtooth wave energy, means to convert the derived portion of energy into direct current energy, means to supply the direct current energy to the anode, and means interposed between said deriving means and converting means to reduce the energy supplied to the anode in the event that said interposed means is touched by a person.

ERNST BUSSE. 

